As Wednesday's non-waiver Trade Deadline approaches, contenders are maneuvering for infusions of late-inning relief. Setup men are baseball's version of offensive linemen, the laborers who quietly keep games safe for the celebrated closer -- or hear about it from the fans if they don't.

"Games can be won and lost in the seventh inning or the fifth inning," said the Yankees' David Robertson, whose job is to hand off to the best closer ever, Mariano Rivera. "The bullpen's got to do the job, to keep the momentum going.

"You keep the same mindset no matter what inning you're pitching. The only difference is in the ninth inning, there's no one else behind you."

The demand for back-end relief is so intense that the Rays acquired Jesse Crain from the White Sox even though there's no assurance he'll rebound from a sore right shoulder. The Dodgers lassoed free agent Brian Wilson, the Giants' colorful and successful 2010 closer who has appeared in just two games the past two seasons in recovery from Tommy John elbow reconstruction surgery.

The Braves looked west, the Angels delivering Scott Downs to fortify a bullpen that has been the envy of 29 other clubs with setup artists Jonny Venters and Eric O'Flaherty cleaning up messes in front of dominant closer Craig Kimbrel.

That was before the baseball gods succeeded where hitters failed in breaking up "The Untouchables," as the trio came to be known. Venters and O'Flaherty submitted to Tommy John reconstructive surgery.

Downs arrived in Atlanta to join another ex-Angel, Jordan Walden, and lefty Luis Avilan in front of Kimbrel. Downs picked up a win in his debut on Monday.

The Orioles also have been looking to former Angels for late-game intervention. They added Francisco Rodriguez -- the all-time single-season saves leader -- in a deal with the Brewers to a setup unit that includes ex-Angel Darren O'Day. The sidewinder's 2.30 ERA is fourth best among setup men since 2009, behind O'Flaherty, Mike Adams and Venters.

The Tigers filled a gnawing void by landing Jose Veras from Houston, where he was 19-for-22 in save chances and holding hitters to a .192 batting average.

Well stocked in the bullpen, the Padres have been listening to proposals for setup men Luke Gregerson and Dale Thayer. Since 2009, Gregerson is tied with Adams for the most holds with 120. Rounding out the top 10 are Matt Thornton, Robertson, Downs, Joel Peralta, Tyler Clippard, O'Flaherty, Joaquin Benoit and Sean Marshall.

The Reds have been patching up the seventh and eighth innings in front of Aroldis Chapman with Marshall and Jonathan Broxton sidelined.

Contenders loading up for the stretch run understand how vital those final six to nine outs are in this era of carefully monitored pitch counts for starters.

Long gone are the days when a glare from Bob Gibson or Don Drysdale could keep a manager anchored in the dugout, watching his star finish what he started.

The upshot of the new game, with fewer innings from starters, is an increased workload for those rubber arms working the sixth, seventh and eighth innings.

Venters (85), Kimbrel (79) and O'Flaherty (78) all ranked in the top five for appearances during the 2011 season that ended with the Braves' September collapse.

The problem, as embodied by Atlanta, is that rubber often burns out. Sending arms out for repairs creates the need for general managers under the gun to pull the trigger on Trade Deadline deals.

While the closer draws the lion's share of the media attention, a quality setup man can be just as valuable to a team and essential to the emotional stability of a manager.

When he was notching his record 62 saves for the 2008 Angels, Rodriguez relied on Scot Shields, who might have been the best setup man ever. Over a six-year stretch ending in 2009, Shields used his deadly sinker and slider to lead the Majors with 149 holds -- 12 more than runner-up Scott Linebrink.

"Scot could come in to put out a fire in the seventh and then pitch the eighth and hand it over to Frankie," Angels manager Mike Scioscia said. "It's a great comfort when you have a setup man as good as Shieldsy was. The closer gets the attention, but the setup guys can be just as important."

A category -- holds -- was designed to identify the premium setup men, who generally can be found on winning teams. There is a connection.

The MLB leader in holds is the Rays' Joel Peralta, with 27, one more than the Pirates' Mark Melancon, who was once considered the Yanks' closer of the future. Robertson and the Cardinals' Trevor Rosenthal have 24 holds, with another Rays reliever, Jake McGee, fifth.

Tampa Bay manager Joe Maddon is hoping Crain, in the midst of a superb season with a 0.74 ERA, can add even more depth to the Rays' relief corps.

Downs took 18 holds and a 1.76 ERA to Atlanta, which envisions a new version of O'Flaherty and Venters. Along with 16 holds, Avilan owns a 1.29 ERA and has held hitters to a .158 batting average. Only the Nationals' Tyler Clippard (.135) and emerging Dodgers setup artist Paco Rodriguez (.136) have been harder to hit among relievers.

Robertson was grateful to Tigers manager Jim Leyland for placing the focus on setup men in the American League All-Star Final Vote this year. Robertson graced the ballot along with Toronto's Steve Delabar, Detroit's Joaquin Benoit, Texas' Tanner Scheppers and Boston's Koji Uehara. Delabar prevailed.

Clearly, it makes fiscal sense to promote from within rather than going to the free-agent market and paying the going rate -- in excess of $10 million -- for a proven closer.

Setup roles have been used to groom some of the best closers. K-Rod set up for Troy Percival with the 2002 champion Angels. Rivera got his training setting up for John Wetteland with the 1996 World Series champion Yankees. Trevor Hoffman, whose career saves record was eclipsed by Rivera, was setting up in Florida when the Marlins sent him to the forever-indebted Padres as part of a package for Gary Sheffield in 1993.

Rivera will be a challenging act to follow for Robertson, presumably his heir apparent.

"If I get the opportunity, yeah, I'd be excited," Robertson said. "Here in New York, we've never had to worry about the ninth inning with Mariano. He's like a staple, like Derek Jeter. You don't know what it'd be like without guys like that."

Lyle Spencer is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.